Among Adelard of Bath, John of Seville, Gerard of Cremona (1114–1187) and Plato of Tivoli (1134–1145) Herman is the most important translator of Arabic astronomical works in 12th century and populariser of Arabic culture in Europe. The influence of his translations on the development of medieval European astronomy was especially large.

Most likely he went to a Benedictine monastic school in Istria. He went on to study in France. It was probably in France that Herman's attention was drawn to the classical texts which were becoming available via Arabic sources. This was before the time of the first university in France, but at Chartres he attended one of the cathedral schools which were the predecessors of universities and he also studied in Paris in the 1130s. The teachers at Chartres included Thierry of Chartres to whom Herman was to dedicate a translation in 1143. The school of Chartres was known for its interests in Christian platonism and the natural sciences.

One of Herman's fellow students in France was Robert of Ketton with whom he travelled for four years in the Eastern Mediterranean. Both men became translators from the Arabic. At Constantinople and Damascus Herman took note of the Arabic science of that period. Circa 1138 he returned to Europe, and was active as a scholar in Spain (an important country for translations from the Arabic) and southern France. A huge part of his work remained anonymous.

In 1142 Herman was in Spain and became involved in an important project to translate Islamic texts. Peter the Venerable recruited a team, including Herman, to translate five texts about Islam into Latin. Different members of the team appear to have concentrated on different works, and Herman is credited as the main translator of two of them: De generatione Muhamet et nutritura eius and Doctrina Muhamet.

The most significant translation in the collection was that of the Qur'an. This was entitled Lex Mahumet pseudoprophete and was the first known translation of the Qur'an into a European language. Robert of Ketton was its principal translator, according to most sources (including the Lex Mahumet pseudoprophete itself). However, Herman may have had some input, given the team nature of the project. Despite being an imperfect translation, Lex Mahumet pseudoprophete remained the standard one for centuries, circulating in manuscript before being printed in the 1543 edition published in Basel by Theodor Bibliander. In this edition both Herman's above-mentioned translations of treatises about Islam appeared together with a preface by Martin Luther.

Herman translated it from an Arabic translation from the Greek (jointly with commentaries of Maslamah Ibn Ahmad al-Majriti, who worked in Córdoba in the 10th century). Western European scholastics became aware of Ptolemy's astronomical views via this translation dedicated to Thierry of Chartres. (This translation was for a long time believed to be the only surviving link to Ptolemy's original. Later another Arabic translation was found to have been preserved in Istanbul).

Herman also translated Ptolemy's Canon (Canon of Kings). For long many thought that Ptolemy was translated by German Herman Contractus and not by Herman of Carinthia.

Herman's first known translation was the sixth book of an astrological treatise Liber sextus astronomie by the Jewish writer Sahl ibn Bishr. It was released in Spain in 1138 under the title Zaelis fatidica (Prophesy). Sahl ibn Bishr had been writing in the Greek astrological tradition. Ibn Bishr's first five books were preserved in the translation of John of Seville (Johannes Hispanus) (circa 1090 – circa 1150). The sixth book deals with three thematic topics regarding the influences on the world and its inhabitants. The work contains divinations based on the movements of the planets and comets.

Circa 1140 Herman translated into Latin the astronomical work of Abu Ma'sharKitab al-madkhal ila ilm ahkam al nujum (Introduction to Astronomy).[1] The work contains problems from Greek philosophy, Arabic astronomy and Eastern astrology, and was first translated into Latin by John of Seville in 1133. Herman's less literal translation was published several times under the title Liber introductorius in astronomiam Albumasaris, Abalachii (Augusta Vindelicorum, Augsburg 1489; Venice 1495 and 1506). A large part of Herman's translation was copied into Roger of Hereford's Book of Astronomical Judgements.

Charles Burnett (2001) postulates that Herman collaborated with Robert of Ketton and Hugo of Santalla on the Liber novem iudicum (the Book of Nine Judges), a collection of translations of Arabic astrologers, notably al-Kindi. Their project may have been to supplant the current superstitious Latin astrology with Arabic astronomical science. Arabic texts cite often Hermes as an authority. Burnett postulates that Renaissance magi merely continued this Hermetic tradition begun by Herman, Robert and Hugh. Herman shares technical terminology with Hugh and a penchant for evocation of the Asclepius, most notably in De essentiis (see below)

His original contribution to philosophy was De essentiis (On essences).[2] In this work Herman deals with five Aristotelian categories (causa, motus, spatium, tempus, habitudo). He started to write this treatise in 1143 in Toulouse and he completed it the same year in Béziers.[3] In 1982 this book was reprinted in Germany.

Some other works are believed to be Herman's:

meteorological Liber imbrium (A book about precipitations) (1140 to 1141)

In the text (or a manuscript, the syntax of this article was not clear) of De indagatione cordis there are many names of scientists and scholars whose work Herman knew and used: Abu Mas'har (787–886), Sahl ibn Bishr, Aomar Tiberia, Abu al-Kindi (801–873), the eighth-century Jewish astrologer Al Batrig Mashallah (Messahalla), Hermes, and Dorotheos of Sidon.

mathematical and astronomical De mensura, De utilitatibus astrolabii, De compositione et usu astrolabii (before 1143 – Herman was certainly interested in the Astrolabe – the portrait shows Herman with one)

Many medieval authors refer to Herman's work, for instance Albert the Great (Albert von Bollstädt, Albertus Magnus), instructor to Thomas Aquinas, in his work Speculum astronomiae.

De indagatione cordis. The complete Latin text was made available in a critical edition by Sheila Low-Beer in her doctoral dissertation Herman of Carinthia: The Liber imbriam, The Fatidica and the De indagatione Cordis, The City University of New York.

Burnett, Charles S. F. (1981). "Hermann of Carinthia and the Kitāb al-Isṭamāṭīs: Further Evidence for the Transmission of Hermetic Magic". Journal of the Warburg and Courtauld Institutes. Vol. 44.

Burnett, Charles S. F. (1976). "The Legend of the Three Hermes and Abū Ma'shar's Kitāb al-Ulūf in the Latin Middle Ages". Journal of the Warburg and Courtauld Institutes. Vol. 39.